An instrument for experiments in mechanics, most probably among the first group of instruments in the Physics Laboratory donated by Charles Emmanuel III to Father Cossu (1764) in a note in which there also appears un piano inclinato con quarto di cerchio .It is composed of a rectangular pane of glass (length 50 cm, width 17 cm) connected at one end to a wooden support with brass hinges so that it can be raised. The other end is connected to a raising device with a screw and crank handle inserted in the support. The inclination, from 0 to 60 degrees, can be read on a metal arc fixed laterally to the support (the quarter of a circle in the note accompanying the instruments sent to Father Cossu).Calibration of the instrument can be performed by means of levelling screws on the wooden feet of the support (height 11.5 cm), with the use of a plumb-line fixed to the upper end of the graduated arc and passing through a small hole in a small metal bracket attached to the support.A brass carriage with two freely turning wheels can roll down the slope, raising light weights or roll up the slope on being pulled by the weights. The carriage and the small platform on which the weights are placed are connected by means of a string running through a pulley at the end of a rod fixed to the top of the inclined plane in such a way as to allow vertical movements of the platform with the weights. An identical instrument is to be found at the Machiavelli Lycée in Lucca.